It is known to use air-drying alkyd resins having high acid numbers for the production of aqueous lacquers and other film-forming agents. Such alkyd resins, having high acid numbers, have good water solubility in the form of their amine salts. Such alkyd resins and film-forming systems based thereon, have the disadvantages of unsatisfactory resistance to water and water vapor, and contain considerable amounts of volatile amines and often toxic auxiliary solvents. While drying and curing, layers formed from such high acid number resins release their amines and solvents which are undesirable sources of pollution to the adjacent atmosphere. To reduce such pollution, it is often necessary to carry out such steps in specially designed apparatus to trap and recover these toxic substances. Such apparatus is expensive and the cost of such apparatus overshadows any savings from the recovered solvents.
It is also known to modify film-forming materials by the incorporation of hydrophilic groups, particularly polyethylene glycol chains into the resin molecule in such a manner that self-emulsifying alkyd resins or melamine resins result.
It is also known that even without direct incorporation into the resin molecule, it is possible to use polyglycol ether derivatives, such as the adducts of ethylene oxide with fatty alcohols, as low molecular-weight, nonionic emulsifiers. In such cases, however, portions of the hydrophilic radical remain active in the film. Due to the hydrophilic nature of the remaining active radical, the resultant film possesses a susceptibility to water penetration. A marked reduction in the hardness of the resultant film is also noted.